SPT SPT avinashcivilengg (Civil/Environmental) (OP) 3 Jan 16 04:41 What it mean that after increasing the intrusive element in soil MDD and OMC get reduces or vice versa? RE: SPT Ron (Structural) 3 Jan 16 13:52 What is the source and context of the statement? Is "intrusive element" defined? Many variables can change the MDD and OMC of a soil. RE: SPT killswitchengage (Geotechnical) 6 Jan 16 18:17 could you explain MDD and OMC ? RE: SPT Ron (Structural) 7 Jan 16 02:58 killswitchengage.... MDD is maximum dry density as determined by a moisture-density relationship test such as the standard or modified Proctor test OMC is the optimum moisture content, the other parameter of the moisture-density relationship test. RE: SPT Riggly (Geotechnical) 21 Jan 16 21:11 What I understand is that a material is introduced into the soil matrix which will increase or decrease the maximum dry density of the soil mass, and the optimum moisture content. I am trying to make sense of this statement. If a material is introduced in the soil matrix that can fit within the voids, density can be increase and the moisture will be displaced. The net effect is that the maximum dry density will increase, but optimum moisture (moisture at which maximum density is achieved for the given energy level imparted) will be decrease. The converse may also be true depending on the nature of the material being introduced into the soil matrix.